Difficulties may be involved in parking vehicles that are equipped with powerful engines and automatic transmissions into a parking space and maneuvering them, depending on the upgrade/downgrade or the engine characteristics. For example, when maneuvering a vehicle rearwards into a parking space on a sloping road, it is often difficult for the driver to adjust the vehicle speed by way of the accelerator pedal in a manner which permits a safe and unproblematic parking maneuver. It is frequently necessary to simultaneously apply the accelerator pedal and the brake pedal in order to smoothly maneuver the vehicle during the parking procedure. Undesirable vehicle reactions may frequently occur which demand too much from the driver or at least render maneuvering difficult.
DE 33 34 723 describes a device for controlling an engine and/or an automatic transmission of automotive vehicles which includes an engine maneuvering control device containing a maneuvering program by which the bottom control range of an accelerator pedal, for low vehicle speeds or engine rotational speeds, is associated with an adjustment travel of the accelerator pedal which is increased compared to the normal operation.
JP 62-255252 discloses a method of controlling the creeping speed of vehicles wherein signals from sensors for the engine rotational speed, the accelerator pedal and the parking brake are sensed and evaluated, and wherein when conditions for creeping speed prevail, the engine or the brakes of the vehicle are controlled correspondingly.
An object of the present invention is to provide a maneuvering assistance system for automotive vehicles and a method of maneuvering automotive vehicles which permit moving the vehicle in a low-speed range in a load-independent, safe and unproblematic way.
According to the present invention, the maneuvering assistance system for automotive vehicles includes an acceleration pedal sensor for determining an accelerator pedal position .alpha.. Further, it may comprise a device for determining a vehicle speed v.sub.ref and there may be provision of a control unit which receives the accelerator pedal position .alpha. and the vehicle speed v.sub.ref. The control unit may either infer from the detected accelerator pedal position .alpha. and the vehicle speed v.sub.ref whether the vehicle is in a maneuvering condition, or the control unit may receive such an information by way of an additional input which is e.g. initiated by the driver. Of course, it is also possible to combine the above-mentioned input information to conclude that a maneuvering condition prevails. When the control unit has detected a maneuvering condition, a drive assembly and/or a brake control system can actuate the vehicle in such a manner that it is moved at a maneuvering speed.
The maneuvering assistance system of the present invention may assume that a maneuvering condition prevails when the accelerator pedal position .alpha. is inferior, or equal to, a limit value .alpha..sub.limit, when a first derivative .alpha. of the accelerator pedal position {character pullout} is inferior, or equal to, a limit value .alpha..sub.limit, and/or when the vehicle speed v.sub.ref is inferior, or equal to, a limit value v.sub.limit.
In addition, the control unit can take into account as a condition for the existence of a maneuvering condition that a second derivative .alpha. of the accelerator pedal position .alpha. is inferior, or equal to, a limit value .alpha..sub.limit.
Thus, the present invention favorably permits determining from sensed signals of the accelerator pedal position .alpha. and/or the vehicle reference speed v.sub.ref whether there is a maneuvering condition, i.e., whether the driver desires to perform a parking procedure, for example. Especially, such a parking procedure may be inferred when the driver depresses the accelerator pedal only to a small extent, the speed of depression of the accelerator pedal is low and, in addition, the vehicle speed is below the above-mentioned limit value. When a parking procedure was detected, a so-called low speed maneuvering (LSM) prevails. This LSM control may then be influenced by the driver either by way of single-pedal operation or two-pedal operation.
In the single-pedal operation, a sensed application of the accelerator pedal corresponds to an adjustment of the maneuvering speed, and release of the accelerator pedal corresponds to deceleration of the vehicle, along with a related actuation of a parking brake when the vehicle speed v.sub.ref =0. Thus, the driver can control the parking procedure only by application of the accelerator pedal, and the vehicle slows down automatically when the driver takes his/her foot from the accelerator pedal and, in addition, the parking brake is activated automatically when the vehicle is at standstill. The maneuvering speed can be maintained constant in this arrangement, irrespective of which accelerator pedal position is chosen by the driver (of course, within the above-mentioned limits of 0&lt;.alpha.&lt;.alpha..sub.limit).
Another variant would imply adapting the maneuvering speed to the extent of depression of the accelerator pedal by way of a corresponding function. However, this would also be executed only within the above-mentioned limits (0&lt;.alpha.&lt;.alpha..sub.limit).
With a two-pedal operation, a sensed application of the accelerator pedal corresponds to the adjustment of an acceleration of the vehicle, a non-application of the accelerator pedal and of a brake pedal corresponds to maintaining the maneuvering speed constant, and an application of the brake pedal corresponds to a reduction of the maneuvering speed, along with a related actuation of a parking brake when the vehicle speed v.sub.ref =0.
As described above, an effective and simple control of the parking procedure can be performed both by the single-pedal operation and the two-pedal operation, with a subsequent actuation of the parking brake when the parking procedure is completed.
It should be noted in particular that the entire parking procedure is absolutely independent of load. This means that e.g. in the presence of a major gradient (positive and/or negative gradient, with a high vehicle weight, etc.), the same parking speed is adjusted by the LSM controller as on flat grounds and with a completely unloaded vehicle. This provides the driver with an auxiliary module which enables him/her to safely maneuver and/or pull the vehicle into a parking space in every situation.
Further, the maneuvering characteristics of the vehicle may approach a normal characteristics which corresponds to the current vehicle performance at rising vehicle speeds v.sub.ref with more depressed accelerator pedal positions a, and/or with quicker accelerator pedal applications .alpha.. This means in particular that, for example, with an accelerator pedal speed 0&lt;.alpha.&lt;.alpha..sub.limit the maneuvering characteristics still further approaches the normal characteristics at rising accelerator pedal application speeds. Especially, another degree of freedom is thereby introduced which achieves additional possibilities of adaption of the maneuvering characteristics. This renders it possible to softly adapt the vehicle reactions, i.e., to achieve a smooth transition between the maneuvering characteristics and the normal characteristics of the vehicle. The term `vehicle reaction` means a reaction of the vehicle caused by inputs of the driver.
Further, there may be provision of a selection device for selecting a maneuvering condition according to the present invention. Such a selection device would e.g. be a switch, a push button, or a similar element, which will be actuated by the driver when he/she wishes to maneuver the vehicle. The maneuvering condition desired by the driver can then be detected by the control unit, and an LSM operation may be performed. When the vehicle is in such an LSM condition, the driver could just as well fully depress the accelerator pedal, and the vehicle would pull into the parking space at the maneuvering speed chosen. Of course, the maneuvering speed could also be adapted between a slightly depressed accelerator pedal position and the maximum depressed accelerator pedal position, and the maximum predetermined maneuvering speed would be adjusted with the maximum depressed accelerator pedal position. Of course, the above-mentioned selection device for selecting a maneuvering condition could also be combined with the above-mentioned detection possibilities for the maneuvering condition.
Further, a ranging sensor may be provided according to the present invention which slows down the vehicle when a minimum distance from an obstacle, for example, another vehicle, is reached, with the parking brakes being then activated automatically.